The present invention relates to a device for adjusting the height of a seat which is mounted in an automotive vehicle or like vehicle and, more particularly, to a height adjusting device for a vehicle seat of the type capable of raising or lowering only a front part of the seat to adjust seat inclination or both the front part and a rear part to adjust the level of the whole seat as desired.
In a vehicle such as an automotive vehicle, a driver's seat should preferably be furnished with instrumentations for various kinds of adjustment in order to ensure a wide visual field and a stable driving position. For example, it is desirable that the height of the whole seat be adjustable to offer a wide visual field with no regard to the eye-point which differs from one person to another due to different body dimensions. It is also desirable the the height of a front part of the seat be controllable independently of a rear part to adjust the seat to an inclination which stably supports any particular operator's body in an optimum driving position. Hereinafter, the adjustment of the whole seat and that of the seat front part will respectively be referred to as height adjustment and lifter adjustment for brevity.
To meet the above demands, some modern seats for use with vehicle are equipped with a seat height control device which fulfills both the height adjustment and the lifter adjustment. A seat height control device of the kind known in the art generally comprises a seat-front support mechanism and a seat-rear support mechanism which support respectively a front part and a rear part of a seat while allowing them to be moved up and down. The seat-front and seat-rear support mechanisms are operated independently of each other.
Japanese Unexamined Patent Publication (Kokai) No. 54-110065, for example, discloses a seat height control device in which the seat-front and seat-rear support mechanisms each comprise a toothed plate which is constantly biased upwardly by a spring, and a link. A pin is associated with each of the toothed plates and actuated by a handle into and out of engagement with its associated toothed plate. With such a device, one may raise a seat front part for lifter adjustment by manipulating the handle associated with the seat front support mechanism, or raise a seat front part and a seat rear part at the same time for height adjustment by manipulating both of the handles.
The problem with such a prior art seat height control device is that the height adjustment is unattainable unless the two handles are operated one after the other, resulting in awkward manipulation. Another problem is that the two handles which have to be positioned near the seat are undesirable considering a limited space available within a vehicle compartment.
Moreover, since the handles simply play the role of locking and unlocking their associated support mechanisms and not the role of directly raising and lowering the seat, a manipulated amount of each handle has no relation with a raised or lowered amount of the seat. Hence, the weight and other loads which the seat bears have to be adjusted in the course of the adjustment of the seat height; adjusting the seat to an optimum height in such a manner is very time-consuming.